The present invention relates generally to equipment utilized and operations performed in conjunction with subterranean wells and, in an embodiment described herein, more particularly provides a perforating gun gravitational orienting system.
It is sometimes desirable to perforate a well in a particular direction or range of directions relative to the wellbore. For example, in a deviated, inclined or horizontal well it is frequently beneficial to shoot perforating charges in a downward direction. However, certain circumstances may instead make it more beneficial to perforate in an upward direction, in a particular inclination from the upward or downward direction, or in another combination or range of directions.
To achieve this goal of perforating wells in particular directions, several attempts have been made to achieve reliable orientation of perforating charges downhole. Unfortunately, each of these has its drawbacks.
One method of orienting perforating charges downhole requires the charges to be rigidly mounted in a gun carrier so that they are pointed in the desired direction(s) relative to the carrier. The gun carrier is then conveyed into a wellbore and either laterally biased physically to one side of the wellbore so that the gun carrier seeks the lower portion of the wellbore due to gravity, or the gun carrier is rotatably supported with its center of gravity laterally offset relative to the wellbore.
This method relies on the gun carrier rotating in the wellbore, so that the gun carrier may be oriented relative to the force of gravity. Frequently, such orienting rotation is unreliable due to friction between the gun carrier and the wellbore, debris in the wellbore, etc.
Another method of orienting perforating charges rotatably mounts the perforating charges in the gun carrier. The charges are mounted to a structure which extends substantially the length of the gun carrier. Rotating supports are attached at each end of the structure to permit the charges and the structure to rotate within the gun carrier due to gravity. Unfortunately, the structure is somewhat complex to assemble and requires use of non-standard gun components, thereby complicating the logistics of providing the orientation system, and failing to take advantage of economies of scale.
Therefore, it may be seen that an improved oriented perforating system is needed.